Some very general adjectives used to describe Slytherin dress are: elegant, stylish, tasteful, alluring, mysterious.
Most Slytherins are very conscious of their outward appearance, and often use styles of clothing/makeup to convey an incredibly situation-specific persona to best suit their personal interests, the goal generally being to make people both impressed by and comfortable with you (the word “chameleon” comes to mind).
An example: say a Slytherin wants to walk into a bank and apply for their first credit card, no prior credit established, new bank, new town
(totally not talking about my weekend). Said Snake would take an extra amount of time that morning to make sure they appear reputable; say, wearing a nice button-up shirt with a pair of well-fitting jeans and carefully styled hair, or maybe a modest dress with pearl earrings and intentionally natural-looking makeup. The goal here is to get the teller to see you as someone who looks good and takes care of themselves, and by extension their finances. Whether or not you deserve what you are looking for is irrelevant; it’s all about using your cunning to use whatever you can to get what you want.
Any of you other Snakes have anything to contribute?
I hope I helped!